Our growing community of microbiologists has developed an outstanding environment for mentoring pre- and postdoctoral trainees in prokaryotic biology. This effort is now producing highly qualified individuals to meet national and international priorities related to bacteriology and to the growing problems of emerging and re-emerging bacterial diseases. Given the growth of our program, both in terms of faculty and trainees, we resubmit this proposal to establish a new NIH-supported Training Program in Bacteriology at the University of Pennsylvania. The Training Program would support 2-3 Ph.D. candidate predoctoral fellows as well as one postdoctoral fellow per year, enabling them to obtain an in-depth experience in any one of 12 laboratories directed by principal investigators who study important aspects of bacterial physiology or diseases of humans, animals or plants. The trainers associated with this T32 proposal have been selected because their research programs in these areas are well established, being supported by NIH or other federal grants and/or having published extensively on these topics. One of the strengths of the prokaryotic community is a diversity that has already fostered productive scientific interactions between three Schools and six Departments at this leading research university. The group of trainers encompasses the major areas of research on bacteria including bacterial-host interactions of leading extracellular (Weiser, S. pneumoniae and H. influenzae;Binns, A. tumefaciens;Yuk, Bordetella spps;Zhu, V. cholerae;and Schifferli, E. coli and V. pestis) and intracellular (Goldfine, L. monocytogenes;Rubin, M. tuberculosis) pathogens, the development of novel vaccines (Paterson, Schifferli and Weiser), immunopathogenesis and use of bacteria as agents in immunotherapy (Paterson, Shen, Yuk), the structure and function of key components bacterial cell surface (Goulian, Daldal, Pohlschroder) and bacterial signaling of target cells (Binns, Goulian, Yuk, Zhu). These trainers have together published articles on over twenty-two bacterial species in the past eight years, which, in conjunction with the breadth of research topics and techniques available in their laboratories, offers numerous research opportunities for current and future trainees. The research opportunities provided by the trainers coupled with strong institutional commitment and an extensive and well-organized training program promises to provide excellent training in bacteriology to both students and postdoctoral fellows.